Cadw said youths were drinking on site and vandalising the castle
A 700-year-old castle has been closed to the public after it was targeted by vandals who threw bottles at staff.
Cadw, the assembly government's historic monuments agency, said workers at Flint Castle had also been spat on.
It said it had not been able to guarantee visitors' safety but hoped to meet again on site on Thursday and re-open by the weekend.
But one councillor said Cadw had acted "out of proportion" and that those responsible were a "small minority".
John Wallis, Cadw's site operations manager, said: "Even though Cadw has invested considerable resources at this monument, we cannot at present guarantee the safety of visitors.
FLINT CASTLE TIMELINE
1277 Work starts on Flint Castle, which was the first in a ring of fortresses built in Wales by Edward I, and building continued until 1286. The keep walls are 23ft thick.
1282 Dafydd ap Gruffydd, brother of Llywelyn the Last, laid siege to the castle
1294 The castle constable burned the fortress to prevent capture by another Welsh army led by Madog ap Llywelyn
1399 The captured Richard II is handed over to Henry Bolingbroke, the future Henry IV at the castle before he is deposed. The "castle's totter'd battlements" were recreated by Shakespeare for a scene in his play about the king
1647 Fell after a three month siege by parliamentarian forces during the English Civil War
"Therefore we have found it necessary to close this site until further notice.
"We are extremely frustrated with the ongoing spate of vandalism.
"Youths are behaving inappropriately, continuing to drink on site even though it's an alcohol-free zone, smashing bottles and threatening staff.
"Despite Cadw having a cleaning regime in place and despite the best efforts of our staff, we are being severely tested. Even the cleaners are spat upon and having bottles thrown at them.
"We are seeking an urgent meeting with the police and the town and county councils to address the problems and try to tackle these issues together.
"All parties need to make a concerted effort to put an end to this harassment."
The castle has been looked after as a public monument for the last 90 years.
Councillor Ian Roberts said he agreed there was "no way staff should have to put up with abuse," but questioned the reasons behind the closure.
He said: "This amounts to a six-day closure, and the furore it's caused is way out of proportion to the incident that occurred.
"I have been told that Cadw closed the castle last Thursday, and plan to re-open it this Thursday, a week later.
"During that time, a few hundred people attended the Big Dee Festival there on Saturday.
"It begs the obvious question, is it safe or isn't it?"
Mr Roberts called into question Cadw's stewardship of the castle, saying it was low down the body's list of priorities.
He said Cadw's handling of the situation might be seen as an "attack" on the local community, adding: "We're talking about a very small minority of people who abuse the castle. The vast majority are proud of it and appreciate the history there."
Alex Aldridge, of Flint Town Council, said it would have been better if Cadw had contacted the council, county council and police to try and find a solution.
Vicky Perfect, a fellow town councillor and the key-holder for the castle, said as far as she was concerned, the castle was closed due to works to take foliage and vegetation off the stonework and not because of vandalism.
She says she has opened up for Cadw since 1983 and had never been spat at or abused, while young people drinking near the castle was a minor problem.
Ms Perfect said she was asked by Cadw to put up a notice saying "closed due to vandalism" when it shut a week and a half ago, which coincided with work starting at the castle too.
Cadw said it took the closure decision on 12 August - after the foliage removal work was completed - and would visit the site on Thursday with the hope of reopening it ahead of the bank holiday weekend.
"The organisers of the Big Dee Festival agreed to undertake a recce of the site prior to the event and carry out any clean up necessary," said a spokesman.
"Cadw has been in close contact with the police since the closure and expect to continue to work with them and others in order to make the castle a place to be enjoyed by the local community and for visitors from further afield."
North Wales Police said: "We were disappointed that we weren't notified of the closure. However, we have now got a meeting with Cadw and we are looking forward to working with them."
Anyone who witnesses anti-social behaviour at the site is asked to call 0845 6071001 (Welsh language) or 0845 6071002 (English).